Testing of pharmacopoeial ethanol (disinfectant ethanol)
Ethanol has antimicrobial properties and is sold as a disinfectant product at optimized concentrations. Quality control of alcohol as a medical product is carried out through verification testing methods stipulated by various pharmacopoeias. As part of an agreement, the procedures for verification testing of ethanol or anhydrous ethanol in disinfectants are roughly the same in the Japanese (JP), United States (USP) and European (EP) pharmacopoeias.
Verification test – component identification via the infra-red absorption spectrum
In the verification testing of ethanol and anhydrous ethanol, identification of components is carried out using Fourier Transform Infrared (FTIR) spectrophotometer. Reference spectra are compared with the spectra of the target compounds. The Japanese Pharmacopeia (JP) specifies a liquid membrane technique test, and below is a measurement example of ethanol and anhydrous ethanol using a liquid cell (KRS-5 window disk).
Purity test – analysis of volatile impurities
Volatile impurities in ethanol are detected with a gas chromatograph (GC). Methanol, acetaldehyde, acetal, benzene, etc. are checked as impurities. An appropriate instrument configuration is required to detect the specified 2 vol ppm limit of trace benzene and obtain good separation for acetaldehyde and methanol (separation of 1.5 or higher). The testing of disinfectant ethanol is covered under the general protocol for purity testing of ethanol.
Chromatogram of Standard Solution for Ethanol for Disinfection (Overlaid Data from Three Continuous Analyses)
UV absorbance test – impurity analysis
The absorbance spectrum of an ethanol sample is used to test for the presence of impurities. A UV-Vis spectrophotometer is used at a wavelength range of 235-340 nm with water as a reference sample. The absorbance at three points (240 nm, 250-260 nm, 270-340nm) is checked as being below certain tolerance values (0.40, 0.30, and 0.10 respectively).
Alcohol Concentration Test for Disinfectants
It is important to control alcohol levels in alcohol-based hand sanitizers in order to ensure constant performance. WHO recommends that hand sanitizers be prepared with an aqueous solution containing 80 % ethanol (v/v) and 75 % isopropyl alcohol (v/v). The section on ethanol for disinfection in the Japanese Pharmacopoeia states that hand sanitizers contain 76.9 ~ 81.4 % ethanol (v/v) (under conditions of 15℃).
USP and JP specify distillation and gas chromatography (GC) as methods for measuring alcohol concentration, with GC able to accurately measure ethanol concentration. A Fourier Transform Infrared (FTIR) spectrophotometer can be used to more easily measure alcohol concentration.
FTIR allows quick and easy quantification of components included in alcohol disinfectants. The contents of ethanol and isopropyl alcohol, which are commonly used in alcohol disinfectants, were measured.
Despite their small footprint, smaller than an A3 size sheet of paper, these models have been engineered with a wide sample compartment that accommodates existing accessories from Shimadzu and other manufacturers. This capability makes them the smallest (installation footprint) and lightest FTIR spectrophotometers in the world that can be used with optional products from other manufacturers.
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The UV-1900i is a double-beam UV-Vis Spectrophotometer using Shimadzu's original LO-RAY-LIGH™ diffraction grating technology. This instrument can not only run checks for nine JIS items, but also those stipulated in the Japanese Pharmacopoeia (JP), United States Pharmacopeia (USP), and the European Pharmacopoeia (EP).